Optical information recording-reproducing apparatus

ABSTRACT

There is disclosed an optical card recorder-reader, in which erroneous signal recording, caused by a low-level light beam when it is stopped at a position for a prolonged period between writing and/or reading operation, either by interruping the irradiation, or by reducing the power of irradiation, or by placing the light beam outside the recording area, when the recording or reading operation is not in progress.

This application is a division of application Ser. No. 07/166,802 filedMar. 3, 1988, now pending, which application is a continuation ofapplication Ser. No. 06/812,995 filed Dec. 24, 1985, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical informationrecording-reproducing apparatus, and in particular to such apparatusemploying a card-shaped optical information recording medium.

In the present invention, the optical information recording-reproducingapparatus shall include an apparatus for recording information on amedium as mentioned above, an apparatus for reproducing informationrecorded on such medium, and an apparatus for recording and reproductionof information.

2. Description of the Prior Art

For the purpose of optical recording and reproduction of informationthere are already known disk-, card- and tape-shaped media. Among these,an optical recording medium formed as a card (hereinafter called opticalcard) is considered to have a large demand as a small, light andportable recording medium of a large capacity.

In such optical card, information is recorded as a row of opticallydetectable record pits by scanning a recording track, determined inadvance on the optical card, with a light beam which is modulatedaccording to the information to be recorded and focused to a small spot.In such operation, in order to exactly record the information withoutfailures such as crossing of the rows of record pits, there has beenrequired automatic tracking for controlling the irradiating position ofthe light beam in a direction perpendicular to the scanning direction.Also there has been conducted automatic focusing for precisely focusingthe light beam onto the optical card. Consequently, in order to obtain atracking signal and a focusing signal from the recording track, themodulated light beam has been designed to have a power just below thelevel required for information recording even at the minimum value. Onthe other hand, the reproduction of recorded information has beenconducted by scanning the row of record pits with a light beam of aconstant power not enough for information recording onto the opticalcard.

In the information recording-reproducing means for optical card asexplained above, the scanning with the light beam is achieved byrelative movement of the optical card and the light beam at informationrecording or reproduction. As the recording tracks are formed as plurallinear lines on the optical card, the scanning is conductedintermittently, inevitably involving standstill states of the lightbeam.

If the light beam remains standstill in such conventional apparatus,erroneous signal recording may take place by the accumulation of energyeven with the light beam of the aforementioned level not enough forinformation recording. Such erroneous signal is also detected by thelight beam, causing serious trouble, for example, in track access, anoperation of moving the light beam to a desired track position.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an optical informationrecording-reproducing apparatus not associated with the above-mentioneddrawbacks of conventional apparatus and constantly enabling exactinformation recording and reproduction avoiding erroneous informationrecording in the standstill state of the light beam.

The above-mentioned object can be achieved, according to the presentinvention, by an optical information recording-reproducing apparatus,provided with means for irradiating a card-shaped optical informationrecording medium with a light beam and means for causing relativemovement of the light beam and the medium for recording information onthe medium with said light beam or reproducing information recorded onthe medium, said apparatus comprising means for preventing informationrecording by the light beam when the light beam and medium are not inrelative movement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of an example of an optical card to beemployed in the apparatus of the present invention;

FIGS. 2A and 2B are charts showing the power of the light beam on theoptical card respectively at recording and reproduction;

FIG. 3 is a schematic view showing the mode of scanning with a lightbeam spot on the optical card;

FIG. 4 is a schematic view showing the structure of a first embodimentof the optical information recording-reproducing apparatus of thepresent invention;

FIGS. 5A, 5B and 5C are views showing the recording operation in avariation of the first embodiment;

FIG. 6 is a schematic view showing the structure of a second embodimentof the optical information recording-reproducing apparatus of thepresent invention;

FIG. 7 is a block diagram showing a variation of timer means in thefirst and second embodiments;

FIG. 8 is a schematic view showing the structure of a third embodimentof the optical information recording-reproducing apparatus of thepresent invention; and

FIG. 9 is a perspective view showing the mode of movement of an opticalhead in the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic plan view of an optical card to be employed in theapparatus of the present invention, wherein shown are an optical card 1;plural linear recording tracks 2 formed on the card; a data recordingarea 3 of the recording track to be scanned with a light beam at apredetermined speed; track selecting areas 4, 4' in which a desiredtrack is searched; and a home position 5 of the light beam. In theinitial state, the light beam is stopped at the home position. Forinformation recording or reproduction the light beam moves in the trackselecting area 4 in a direction a to search an N-th track 2 in which theinformation is to be recorded or reproduced. Then the light beam scansthe data recording area 3 of the track 2 in a direction of arrow c torecord or reproduce information. Upon completion thereof, the light beamstops in the track selecting area 4' and remains at a standstill untilsucceeding information recording or reproduction. Then, in response toan instruction for information recording or reproduction, the light beammoves in said selecting area 4' in a direction a, toward a track, forexample (N+ 1)-th, for recording or reproduction, and subsequently scansthe data recording area of said track in a direction of arrow b, thuseffecting information recording or reproduction. The above-explainedsteps are repeated to record or reproduce data of a required amount.

FIGS. 2A and 2B are charts showing the power of the light beam on theoptical card respectively in information recording and reproduction,wherein the abscissa indicates the position on the track while theordinate indicates the power P of the light beam. At informationrecording, as shown in FIG. 2A, the light beam in a scanning range EWcorresponding to the data recording area irradiates the optical cardwith a constant minimum power P_(WL) required for obtaining a trackingsignal and a focusing signal and still not enough for forming recordpits. It is modulated to a power level P_(WH) required for recording inresponse to the signals to be recorded, and the record bits are formedonly in areas irradiated with power P_(WH). At information reproductionthe card is irradiated by the light beam in a scanning range ER with aconstant power P_(R) not enough for forming record pits whereby therecord pits are read.

The recording sensitivity of the optical card is generally determined bythe irradiating power P and irradiating time T of the light beam. Thus,a light beam moving with a relative speed V from 6' to 6 as shown inFIG. 3 is not recorded if V exceeds Φ/T wherein Φ is the diameter of thelight beam spot. However, if the light beam remains in the standstillstate for a long time, there will result an erroneous recording evenwhen the power of the light beam is equal to P_(WL) or P_(R). In thepresent invention it is rendered possible to prevent the erroneousrecording in such a standstill state.

FIG. 4 is a schematic view of a first embodiment of an opticalinformation recording-reproducing apparatus of the present invention,wherein an optical card 1, as shown in FIG. 1, is placed on a support 17fixed to a belt 20, which is provided between pulleys 19, 18 and drivenin a direction d by a motor 21 to displace the optical card 1 indirection d. Consequently a light beam 32 emitted by an optical head 16scans the optical card 1 in the direction b or c shown in FIG. 1. Theoptical head 16 is composed of a semiconductor laser 11, a collimatinglens 12, a beam splitter 13, an objective lens 14 and a photodetector15. The light beam, emitted by the semiconductor laser 11, is focused bythe objective lens 14, as a small spot on the optical card 1. Lightreflected by the optical card again passes the objective lens 14, thenseparated from the entering light by the beam splitter 13 and isdetected by the photodetector 15. A signal detected by saidphotodetector 15 is supplied to a signal demodulating circuit 22, atracking control circuit 23 and a focus control circuit 24, of which thelatter two respectively move the objective lens 14 in the axialdirection and a perpendicular direction thereto for automatic focusingand automatic tracking.

A stepping motor 28 moves the optical head 16 in a directionperpendicular to the plane of drawing, thus displacing the irradiatingposition of the light beam in the direction as shown in FIG. 1. Themotor 21 is controlled by a motor driving circuit 25 to move and stopthe optical card. The driving speed of the motor 21 is detected by aspeed detecting circuit 29 which is connected through a time measuringcircuit 30 to a laser driving circuit 31 for driving the semiconductorlaser 11. Also the signal demodulating circuit 22, stepping motor 28,motor driving circuit 25 and laser driving circuit 31 are connected,through an interface 26, to a central processing unit (CPU) 27.

At information recording or reproduction in the above-describedapparatus, the CPU 27 drives the motor 21 and the stepping motor 28 toscan the data recording area 3 with the light beam as already explainedin relation to FIG. 1. In this operation the power of the light beam 32from the semiconductor laser 11 on the optical card is constantly equalto P_(WL) or P_(R) shown in FIG. 2A or 2B, and is modulated up to alevel P_(WH) in the case of information recording, according to arecording signal entered from a terminal C1. On the other hand, in thecase of signal reproduction, the reproduced signal is released from aterminal C2. Upon completion of the operation, the motor 21 is stoppedso that the light beam remains still with a power P_(WL) or P_(R). Whenthe motor 21 is stopped, the speed detecting circuit 29 identifies thatthe relative speed V between the optical card and the light beam hasbecome equal to zero and activates the time measuring circuit 30 havinga preset time T_(OFF). When the time from the activation becomes equalto the time T_(OFF), an irradiation terminating signal is supplied tothe laser driving circuit 31 to terminate the light emission from thesemiconductor laser 11. The time measuring circuit is reset if acondition V≠0 is reached by a succeeding operation started in a periodt<T_(OFF). The time T_(OFF) is so selected as to satisfy a conditionT_(OFF) <T_(S), wherein T_(S) is the time required for recording with astopped beam of the aforementioned power P_(WL) or P_(R). (For exampleT_(OFF) =T_(S/) 2) Also the preset time T_(OFF) may be rendered stepwisevariable by an external selector switch or continuously variable by avariable resistor according to the recording sensitivity of the opticalcard.

In the foregoing embodiment, the beam irradiation to the medium isinterrupted for preventing erroneous recording in a non-operating state,but it is also possible to reduce the power of the light beam to a levelat which recording is not achieved even if the light beam is maintainedstill for a prolonged period. Such an embodiment will be explained inthe following. The structure of the apparatus in such an embodiment isessentially similar to that shown in FIG. 4 and will not therefore beexplained in detail.

FIGS. 5A, 5B and 5C illustrate the recording operation in thisembodiment, wherein FIG. 5A is an enlarged view of the recording face ofthe aforementioned optical card 1. Between the recording tracks 2_(N),2_(N+1) , . . . of the data recording area 3, there are alternatelyformed tracking tracks 8 for detecting tracking signals and clock tracks7 for obtaining clock signals. Also in the track selecting area 4₁ thereis formed an auxiliary track 9 for maintaining the light beam on thetrack in the non-operating state. FIG. 5B shows the relative speed ofthe light beam and the recording face at positions on the optical cardcorresponding to FIG. 5A, and FIG. 5C shows the power P of the recordinglight beam at these corresponding positions.

In the apparatus shown in FIG. 4, the light beam is in fact divided intothree beams, for example, by an unrepresented grating, and the resultingspots fall on the optical card 1 as shown b S_(1a), S_(2a), S_(3a) orS_(1b), S_(2b), S_(3b) or S_(1c), S_(2c), S_(3c) in FIG. 5A. For thepurpose of clarity, the power of light beam is represented by thediameter of spot in FIG. 5A. At information recording, the light beamscans the recording face with a constant speed V_(W) as shown in FIG.5B, and the information recording is made with the recording beam at thecenter. At the same time lateral spots respectively detect the trackingsignal and the clock signal. The power of the recording beam on theoptical card is modulated between P_(WH) and P_(WL) according to theinformation as shown in FIG. 5C. The powers of the spots S_(2a), S_(2b)are respectively set at P_(WH) and P_(WL). The spots for obtaining theclock and tracking signals are adjusted to low power levels which aresufficient for obtaining the signal but are insufficient for informationrecording.

Upon completion of the recording operation, the beam spots enter thetrack selecting area 4₁, reducing the relative speed to the recordingface as shown in FIG. 5B and stop at the positions s_(1c), s_(2c),s_(3c). In this state, the speed detecting circuit 29 shown in FIG. 4detects that the relative speed V of the light beam and the optical cardhas become lower than limit relative speed V_(L) and activates the timemeasuring circuit 30. The time measuring circuit 30 is provided with apreset time Tc, for example 1 second, and, when the time t becomes equalto Tc, since the condition V<V_(L) is satisfied, a power reducing signalis supplied to the laser driving circuit 31 to control the current tothe semiconductor laser 11 thereby reducing the power of the spot S_(2c)on the optical card to Ps. The spot thus enters a stand-by state inwhich it is maintained on the auxiliary track 9 by detecting thetracking signal with the spot S_(2c). When the operation is startedagain to restore a condition V>V_(L), the speed detecting circuit 29increases the power of the spot to the original state to effect theinformation recording. The above-mentioned power P_(S) of the spotS_(2c) is selected to be the minimum level that is required for trackingand does not record on the medium even after a prolonged irradiation ina standstill state. The time measuring circuit 30 is reset if thecondition V>V_(L) is reached by the start of a succeeding operation. Theaforementioned time Tc is so selected as to satisfy where Ts is thecondition Tc<Ts, a time required for record formation with a stoppedlight beam of a power P_(WL) (for example Tc= Ts/2). Also the presettime Tc may be stepwise regulated by an external selector switch orcontinuously regulated by a variable resistor, according to therecording sensitivity of the optical card. Though FIG. 5C illustratesthat the power P is reduced to Ps as soon as the condition V<V_(L) isreached, there is in fact an interim interval because of the function ofthe time measuring circuit 30.

Though the foregoing explanation is limited to the case of informationrecording, an identical operation takes place also in the reproductionof the information recorded on the optical card, except that a constantpower P_(R) is adopted in the operation shown in FIG. 5C.

In the following there is given an example of the selection of theintensity of the light beam in the foregoing embodiment. In an examplewith a beam spot diameter of 5 μm, a relative scanning speed of V_(W)=50 mm/sec in recording and a relative scanning speed of V_(R) =500mm/sec in reproduction, the recording time T is related with the power Pof the light beam as follows:

Ts=100 μsec for P=5 mW

Ts=1 sec for P=1 mW and

Ts=∞for P=0.2 mW;

the powers of the aforementioned spots S_(2a), S_(2b) can be selectedrespectively as P_(WH) 5 mW and P_(WL) =1 mW. If the power ratio of thecentral spot and lateral spots, which is constant when a diffractiongrating is employed, is selected as 5:1, the powers of the spots S_(3a)and S_(3b) are respectively 1 mW and 0.2 mW. It is assumed in this casethat 0.2 mW is enough for obtaining the tracking signal. Since the limitrelative speed V_(L) for the light beam of 1 mW is equal to V_(L)=Φ/Ts=5 μm/sec, recording is not achieved with a light beam of a powerlower than 1 mW since V_(W) or V_(R) >V_(L) is reached during theoperation. Also if the Tc is selected as 1 second and Ps is selected as0.2 mW, the power of the spot S_(2c) is lowered to 0.2 mW before arecord is formed by said spot on the auxiliary track 9 so that erroneousrecording can be prevented. A similar situation can be attained byselecting a condition P_(R) =1 mW for the reproduction of information.

As explained in the foregoing, in this embodiment, the power of thelight beam is reduced to avoid erroneous recording in the non-operatingstate where the light beam is stopped, and the access time in therestart of operation can be reduced since the tracking control iscontinued in such a standstill state with reduced power.

FIG. 6 is a schematic view of a second embodiment of the opticalinformation recording-reproducing apparatus of the present invention,wherein like components as those in FIG. 4 are represented by likenumbers and will not be explained in detail. As will be seen in FIG. 6,the structure of the present embodiment is almost same as that of thefirst embodiment, except that the signal from the time measuring circuit30 is supplied to the motor driving circuit 25. In the presentembodiment, the time during which the light beam is stopped is measured,and the irradiating position of the light beam on the optical card isdisplaced before an erroneous recording takes place.

In information recording or reproduction in this apparatus, the CPU 27controls the motor 21 and the stepping motor 28 to scan the datarecording area 3 with a light beam as already explained in relation toFIG. 1. In this state the light beam 32 from the semiconductor laser 11constantly has a power P_(WL) or P_(R) on the optical card as shown inFIG. 2, and, in information recording, a modulation up to a power P_(WH)is made in response to the recording signal entered from the terminalC1. At the reproduction of information, the reproduced signal isreleased from the terminal C2. Upon completion of the operation, themotor 21 is stopped whereby the light beam stops in the track selectingarea, with a power level P_(WL) or P_(R). When the motor 21 is stopped,the speed detecting circuit 29 identifies that the relative speed V ofthe optical card and the light beam have become equal to zero andactivates the time measuring circuit 30, having a preset time T_(M).When the time t becomes equal to T_(M), since the condition V=0 isreached an irradiating position displacing signal is transmitted to themotor driving circuit 25, which, in response, activates the motor underthe control of the CPU 27 to displace the irradiating position of thelight beam to the other track selecting area, for example from the area4₂ to 4₁. The time measurement is again started at the new location ofthe light beam, and this procedure is repeated until a recording orreproducing operation is started. On the other hand, the time measuringcircuit 30 is reset if a condition V≠0 is reached by the start of asucceeding recording or reproducing operation within a period t<T_(M).The preset time T_(M) is so selected as to satisfy a condition T_(M)<T_(S), the time required for obtaining a record with a stopped lightbeam of the aforementioned power P_(WL) or P_(R), for example T_(M)=T_(S) /2.

The light beam is moved to the other track selecting area in theforegoing embodiment, but it is also possible to move the irradiatingposition slightly in the same track selecting area. Also the irradiatingposition of the light beam may be displaced in the so-called trackaccess direction, perpendicular to the track direction, instead ofdisplacement in the track direction by the motor 21. In this case theirradiating position displacing signal from the aforementioned timemeasuring circuit 30 is supplied to the stepping motor 28, whereby theirradiating position is moved for example to a neighboring track. Alsoinstead of stopping the light beam at a new position, it is furthermorepossible to dissipate the energy accumulated in the original irradiatingposition during the movement of the light beam and to then return thelight beam to the original position.

FIG. 7 is a block diagram showing a variation of the time measuringmeans employed in FIG. 4 or FIG. 6. In this variation, theaforementioned time T_(OFF), T_(c) or T_(M) is rendered arbitrarilyregulatable in a range shorter than T_(S) by a time setting circuit 32,according to the recording sensitivity of the optical card. The timemeasuring circuit 30, connected to the speed detecting circuit 29,starts time measurement in response to the detection of a condition V=0,and, the measured value and the time selected by the time settingcircuit 32 are supplied to a coincidence circuit 33, which releases anirradiating position displacing signal upon the coincidence of the two.The signal is supplied to the irradiating position displacing means suchas the motor 21 shown in FIG. 6 or to the laser driving circuit 31 shownin FIG. 4, thus displacing the irradiating position of the light beam orregulating the power thereof, as in the foregoing embodiments, under thecontrol of a control circuit 35 such as a CPU. In the time settingcircuit 32, the time is stepwise or continuously regulatable by aselector switch or a variable resistor.

In the foregoing second embodiment the irradiating position of the lightbeam is displaced within the recording area, but it is also possible todivert the light beam from the recording area when the informationrecording or reproduction does not take place, as will be explained inthe following.

FIG. 8 is a schematic view of a third embodiment of the opticalinformation recording-reproducing apparatus of the present invention,wherein like components as those in FIG. 4 are represented by likenumbers and will not be explained in detail.

In information recording or reproduction in the present embodiment, theCPU 27 controls the motor 21 and the stepping motor 28 whereby the lightbeam leaves the home position 6 and scans the recording area as alreadyexplained in relation to FIG. 1. In this state the light beam 32 fromthe semiconductor laser 11 always has a power P_(WL) or P_(R) shown inFIG. 2, and a modulation up to a level P_(WH) is made at informationrecording in response to the recording signal entered from the terminalC1. At information reproduction the reproduced signal is released fromthe terminal C2. Upon completion of the operation, the motor 21 isstopped whereby the light beam stops in the track selecting area, with apower P_(WL) or P_(R). Subsequently the stepping motor 28 is activatedunder the control of the CPU 27, whereby the optical head 16 is moved ina direction d shown in FIG. 9 to divert the light beam 32 from therecording area 2 on the optical card 1 and to stop the same at the homeposition 6. At the re-start of the operation, the above-explainedprocedure is repeated, thus moving the light beam 32 from the homeposition 6 to the recording area 2 for information recording orreproduction.

In the foregoing embodiment the light beam is retracted to the homeposition when the recording or reproducing operation is not in progress,but the light beam may be diverted to any other position outside therecording area. The oscillation of the semiconductor laser may beinterrupted when the light beam is positioned outside the recordingarea, but, in such case, the oscillation is preferably to be startedagain outside the recording area. In this manner it is rendered possibleto prevent erroneous recording, eventually caused by an overshootphenomenon at the termination or start of the laser oscillation.

The present invention is not limited to the foregoing embodiments but issubject to various modifications. For example, though the stopped stateof the light beam in the foregoing embodiments is detected directly fromthe motor, the time measurement may be initiated by a signal from theCPU, controlling the movement of the optical card. Also the speeddetection may be achieved by a signal read by the photodetector. In theaforementioned variation of the first embodiment the power of the lightbeam is reduced, but it is also possible, if a recording takes placewith a minimum power for obtaining the tracking signal after a prolongedperiod, for example an hour, to reduce the power of the light beam inthe non-operating state and then to interrupt the beam irradiation incase a next access is not started within a determined period.Furthermore, the present invention is not limited to the apparatus forinformation recording and reproduction as explained before, but isapplicable also to an apparatus exclusively designed for recording orfor reproduction.

What is claimed is:
 1. A method for intermittently recording and/orreproducing information on or from an optical recording medium having aplurality of tracks, in accordance with control of a controller, themethod comprising the steps of:moving a light beam from a home positionto a desired track on the recording medium; effecting informationrecording or reproduction by scanning the desired track with the lightbeam; placing and maintaining the light beam in a stand-by state inwhich the light beam is applied to the desired track without beingreturned to the home position, after the termination of the informationrecording or reproduction; starting a next information recording orreproduction operation with the light beam being applied to the medium,when the controller commands the next information recording orreproduction operation before the lapse of a predetermined time in thestand-by state; and terminating the application of the light beam to therecording medium, when the controller gives no command for commencingthe next information recording or reproduction operation after the lapseof the predetermined time in the stand-by state.
 2. A method accordingto claim 1, wherein said medium is of a card-like shape and the lightbeam reciprocates relative to said medium at the time of recordingand/or reproducing.
 3. A method for recording or reproducing informationon or from an optical recording medium having a plurality of tracks, themethod comprising the steps of;effecting an information recording orreproduction operation by scanning one of the plurality of tracks with alight beam which reciprocates along a direction of an extension of theone of the plurality of tracks; and terminating the scan of the lightbeam along the direction of the extension of the one of the plurality oftracks to hold the light beam in a stand-still state at an end portionof the one of the plurality of tracks during a period betweentermination of the information recording or reproduction operation andinitiation of a next information recording or reproduction operation. 4.An apparatus for recording and/or reproducing information with a lightbeam on and/or from an optical recording medium having a plurality oftracks, the apparatus comprising:irradiating means for irradiating oneof the plurality of tracks of the recording medium with a light beam;moving means for reciprocally moving the recording medium and the lightbeam with respect to each other so that the light beam and the one ofthe plurality of tracks move relative to each other along a direction ofan extension of the one of the plurality of tracks; and control meansfor operating said moving means during a recording and/or reproductionoperation, and for holding the light beam in a stand-still state at anend portion of the one of the plurality of tracks by terminating theoperation of said moving means, during a period between termination ofthe recording and/or reproduction operation and initiation of a nextrecording and/or reproducing operation.
 5. An apparatus according toclaim 4, wherein said irradiating means comprises a light source and anoptical system for converging the light beam from said light source ontothe recording medium.
 6. An apparatus according to claim 4, wherein saidmoving means comprises a support for supporting the recording mediumthereon and a motor for reciprocally moving said support.
 7. Anapparatus according to claim 4, wherein said control means comprises acentral processing unit.